scholarly journals ENSO drives lateral separation of FAD-associated skipjack and bigeye tuna in the Western Tropical Pacific

2020 ◽  
Author(s):  
Shirley Leung ◽  
K. A. S. Mislan ◽  
LuAnne Thompson
Keyword(s):  
El Niño ◽  
El Nino ◽  
Tropical Pacific ◽  
Sea Surface ◽  
Purse Seine ◽  
Skipjack Tuna ◽  
Bigeye Tuna ◽  
Lateral Separation ◽  
Western Tropical Pacific ◽  
La Nina

AbstractIncidental capture of juvenile bigeye tuna in fish aggregating device (FAD)-associated purse seine fisheries targeting skipjack tuna have contributed significantly to the degradation of bigeye stocks in the Western Tropical Pacific (WTP) Ocean. One way to reduce this incidental catch is to simply limit purse seine fishing effort; however, skipjack tuna stocks are healthy and economically important to many small island nations in the region. Here we assess whether there is sufficient lateral separation of skipjack and bigeye within FAD-associated purse seine fisheries in the WTP to allow limiting bigeye catch while maintaining a robust skipjack fishery. Based on monthly 5°-longitude-by-5°-latitude catch and effort data, FAD-associated bigeye and skipjack catch per unit effort (CPUE) covary tightly throughout the WTP, such that lateral separation between the two species is generally small. There are, however, significant variations in the amount of separation over both space and time. Waters within the Party to the Nauru Agreement exclusive economic zones (EEZs) belonging to Palau, Solomon Islands, and Tuvalu regularly exhibit some of the smallest bigeye-to-skipjack catch ratios, especially during El Niño. In contrast, waters within Kiribati’s Phoenix Islands EEZ regularly exhibit some of the largest bigeye-to-skipjack catch ratios, which are particularly high during La Niña. In general, El Niño lowers bigeye-to-skipjack catch ratios east of 170°E, while La Niña lowers bigeye-to-skipjack catch ratios west of 170°E. These ENSO-driven variations in separability are larger and more widespread than those driven by seasonality, due to larger associated variations in environmental conditions. Sea surface height anomalies may be particularly useful for demarcating the different environments preferred by skipjack and bigeye throughout the WTP. Sea surface temperatures, temperatures at 100 m, and thermocline depths may also help distinguish between the two species’ preferred habitats in many areas. These analyses can help better inform the complex decisions made by both fishers during operations and fisheries managers during creation of effective, dynamic policies to preserve bigeye stocks in the WTP. They also show that climate variability can have substantial effects on the spatial distributions of top pelagic predators and their interactions with one another.

Asymmetric Responses of the Western Tropical Pacific Sea Level to El Niño and La Niña

2020 ◽  
Author(s):  
Fan WANG ◽  
Qiuping Ren ◽  
Yuanlong Li ◽  
Fei Zheng ◽  
Jing Duan
Keyword(s):  
Sea Level ◽  
El Niño ◽  
El Nino ◽  
Tropical Pacific ◽  
La Niña ◽  
Western Tropical Pacific ◽  
La Nina ◽  
Asymmetric Responses

scholarly journals Asymmetry of Interannual Sea Level Variability in the Western Tropical Pacific: Responses to El Niño and La Niña

2020 ◽  
Vol 125 (10) ◽  
Author(s):  
Qiuping Ren ◽  
Yuanlong Li ◽  
Fei Zheng ◽  
Fan Wang ◽  
Jing Duan ◽  
...  
Keyword(s):  
Sea Level ◽  
El Niño ◽  
El Nino ◽  
Tropical Pacific ◽  
La Niña ◽  
Sea Level Variability ◽  
Western Tropical Pacific ◽  
La Nina

scholarly journals Changes in Spread and Predictability Associated with ENSO in an Ensemble Coupled GCM

2006 ◽  
Vol 19 (17) ◽  
pp. 4378-4396 ◽  
Author(s):  
Renguang Wu ◽  
Ben P. Kirtman
Keyword(s):  
Surface Pressure ◽  
El Niño ◽  
El Nino ◽  
Tropical Pacific ◽  
La Niña ◽  
Boreal Summer ◽  
Boreal Winter ◽  
Central Pacific ◽  
La Nina ◽  
Signal Change

Abstract The present study documents the influence of El Niño and La Niña events on the spread and predictability of rainfall, surface pressure, and 500-hPa geopotential height, and contrasts the relative contribution of signal and noise changes to the predictability change based on a long-term integration of an interactive ensemble coupled general circulation model. It is found that the pattern of the El Niño–Southern Oscillation (ENSO)-induced noise change for rainfall follows closely that of the corresponding signal change in most of the tropical regions. The noise for tropical Pacific surface pressure is larger (smaller) in regions of lower (higher) mean pressure. The ENSO-induced noise change for 500-hPa height displays smaller spatial scales compared to and has no systematic relationship with the signal change. The predictability for tropical rainfall and surface pressure displays obvious contrasts between the summer and winter over the Bay of Bengal, the western North Pacific, and the tropical southwestern Indian Ocean. The predictability for tropical 500-hPa height is higher in boreal summer than in boreal winter. In the equatorial central Pacific, the predictability for rainfall is much higher in La Niña years than in El Niño years. This occurs because of a larger percent reduction in the amplitude of noise compared to the percent decrease in the magnitude of signal from El Niño to La Niña years. A consistent change is seen in the predictability for surface pressure near the date line. In the western North and South Pacific, the predictability for boreal winter rainfall is higher in El Niño years than in La Niña years. This is mainly due to a stronger signal in El Niño years compared to La Niña years. The predictability for 500-hPa height increases over most of the Tropics in El Niño years. Over western tropical Pacific–Australia and East Asia, the predictability for boreal winter surface pressure and 500-hPa height is higher in El Niño years than in La Niña years. The predictability change for 500-hPa height is primarily due to the signal change.

scholarly journals The Years of El Niño, La Niña, and Interactions with the Tropical Indian Ocean

2007 ◽  
Vol 20 (13) ◽  
pp. 2872-2880 ◽  
Author(s):  
Gary Meyers ◽  
Peter McIntosh ◽  
Lidia Pigot ◽  
Mike Pook
Keyword(s):  
Indian Ocean ◽  
Surface Temperature ◽  
Sea Surface Temperature ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Sea Surface ◽  
El Nino Southern Oscillation ◽  
La Nina ◽  
The Indian Ocean

Abstract The Indian Ocean zonal dipole is a mode of variability in sea surface temperature that seriously affects the climate of many nations around the Indian Ocean rim, as well as the global climate system. It has been the subject of increasing research, and sometimes of scientific debate concerning its existence/nonexistence and dependence/independence on/from the El Niño–Southern Oscillation, since it was first clearly identified in Nature in 1999. Much of the debate occurred because people did not agree on what years are the El Niño or La Niña years, not to mention the newly defined years of the positive or negative dipole. A method that identifies when the positive or negative extrema of the El Niño–Southern Oscillation and Indian Ocean dipole occur is proposed, and this method is used to classify each year from 1876 to 1999. The method is statistical in nature, but has a strong basis on the oceanic physical mechanisms that control the variability of the near-equatorial Indo-Pacific basin. Early in the study it was found that some years could not be clearly classified due to strong decadal variation; these years also must be recognized, along with the reason for their ambiguity. The sensitivity of the classification of years is tested by calculating composite maps of the Indo-Pacific sea surface temperature anomaly and the probability of below median Australian rainfall for different categories of the El Niño–Indian Ocean relationship.

scholarly journals Improved Simulation of Tropical Cyclone Responses to ENSO in the Western North Pacific in the High-Resolution GFDL HiFLOR Coupled Climate Model*

2016 ◽  
Vol 29 (4) ◽  
pp. 1391-1415 ◽  
Author(s):  
Wei Zhang ◽  
Gabriel A. Vecchi ◽  
Hiroyuki Murakami ◽  
Thomas Delworth ◽  
Andrew T. Wittenberg ◽  
...  
Keyword(s):  
High Resolution ◽  
Tropical Cyclone ◽  
El Niño ◽  
North Pacific ◽  
Western North Pacific ◽  
El Nino ◽  
Walker Circulation ◽  
La Niña ◽  
Sea Surface ◽  
La Nina

Abstract This study aims to assess whether, and the extent to which, an increase in atmospheric resolution of the Geophysical Fluid Dynamics Laboratory (GFDL) Forecast-Oriented Low Ocean Resolution version of CM2.5 (FLOR) with 50-km resolution and the High-Resolution FLOR (HiFLOR) with 25-km resolution improves the simulation of the El Niño–Southern Oscillation (ENSO)–tropical cyclone (TC) connections in the western North Pacific (WNP). HiFLOR simulates better ENSO–TC connections in the WNP including TC track density, genesis, and landfall than FLOR in both long-term control experiments and sea surface temperature (SST)- and sea surface salinity (SSS)-restoring historical runs (1971–2012). Restoring experiments are performed with SSS and SST restored to observational estimates of climatological SSS and interannually varying monthly SST. In the control experiments of HiFLOR, an improved simulation of the Walker circulation arising from more realistic SST and precipitation is largely responsible for its better performance in simulating ENSO–TC connections in the WNP. In the SST-restoring experiments of HiFLOR, more realistic Walker circulation and steering flow during El Niño and La Niña are responsible for the improved simulation of ENSO–TC connections in the WNP. The improved simulation of ENSO–TC connections with HiFLOR arises from a better representation of SST and better responses of environmental large-scale circulation to SST anomalies associated with El Niño or La Niña. A better representation of ENSO–TC connections in HiFLOR can benefit the seasonal forecasting of TC genesis, track, and landfall; improve understanding of the interannual variation of TC activity; and provide better projection of TC activity under climate change.

ENSO-Like and ENSO-Induced Tropical Pacific Decadal Variability in CGCMs

2013 ◽  
Vol 26 (5) ◽  
pp. 1485-1501 ◽  
Author(s):  
Jung Choi ◽  
Soon-Il An ◽  
Sang-Wook Yeh ◽  
Jin-Yi Yu
Keyword(s):  
El Niño ◽  
Decadal Variability ◽  
El Nino ◽  
Tropical Pacific ◽  
Modulation Index ◽  
Subsurface Temperature ◽  
Enso Variability ◽  
Decadal Modulation ◽  
Pacific Decadal Variability ◽  
La Nina

Abstract Outputs from coupled general circulation models (CGCMs) are used in examining tropical Pacific decadal variability (TPDV) and their relationships with El Niño–Southern Oscillation (ENSO). Herein TPDV is classified as either ENSO-induced TPDV (EIT) or ENSO-like TPDV (ELT), based on their correlations with a decadal modulation index of ENSO amplitude and spatial pattern. EIT is identified by the leading EOF mode of the low-pass filtered equatorial subsurface temperature anomalies and is highly correlated with the decadal ENSO modulation index. This mode is characterized by an east–west dipole structure along the equator. ELT is usually defined by the first EOF mode of subsurface temperature, of which the spatial structure is similar to ENSO. Generally, this mode is insignificantly correlated with the decadal modulation of ENSO. EIT closely interacts with the residuals induced by ENSO asymmetries, both of which show similar spatial structures. On the other hand, ELT is controlled by slowly varying ocean adjustments analogous to a recharge oscillator of ENSO. Both types of TPDV have similar spectral peaks on a decadal-to-interdecadal time scale. Interestingly, the variances of both types of TPDV depend on the strength of connection between El Niño–La Niña residuals and EIT, such that the strong two-way feedback between them enhances EIT and reduces ELT. The strength of the two-way feedback is also related to ENSO variability. The flavors of El Niño–La Niña with respect to changes in the tropical Pacific mean state tend to be well simulated when ENSO variability is larger in CGCMs. As a result, stronger ENSO variability leads to intensified interactive feedback between ENSO residuals and enhanced EIT in CGCMs.

scholarly journals A New Picture of the Global Impacts of El Nino-Southern Oscillation

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Jialin Lin ◽  
Taotao Qian
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Tropical Pacific ◽  
Sea Surface ◽  
El Niño Southern Oscillation ◽  
El Nino Southern Oscillation ◽  
Global Impacts

AbstractThe El Nino-Southern Oscillation (ENSO) is the dominant interannual variability of Earth’s climate system and plays a central role in global climate prediction. Outlooks of ENSO and its impacts often follow a two-tier approach: predicting ENSO sea surface temperature anomaly in tropical Pacific and then predicting its global impacts. However, the current picture of ENSO global impacts widely used by forecasting centers and atmospheric science textbooks came from two earliest surface station datasets complied 30 years ago, and focused on the extreme phases rather than the whole ENSO lifecycle. Here, we demonstrate a new picture of the global impacts of ENSO throughout its whole lifecycle based on the rich latest satellite, in situ and reanalysis datasets. ENSO impacts are much wider than previously thought. There are significant impacts unknown in the previous picture over Europe, Africa, Asia and North America. The so-called “neutral years” are not neutral, but are associated with strong sea surface temperature anomalies in global oceans outside the tropical Pacific, and significant anomalies of land surface air temperature and precipitation over all the continents.

scholarly journals Dipole Structure of Mixed Layer Salinity in Response to El Niño‐La Niña Asymmetry in the Tropical Pacific

2019 ◽  
Vol 46 (21) ◽  
pp. 12165-12172 ◽  
Author(s):  
Cong Guan ◽  
Shijian Hu ◽  
Michael J. McPhaden ◽  
Fan Wang ◽  
Shan Gao ◽  
...  
Keyword(s):  
Mixed Layer ◽  
El Niño ◽  
El Nino ◽  
Tropical Pacific ◽  
La Niña ◽  
Dipole Structure ◽  
La Nina ◽  
The Tropical Pacific
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